Andean man resides in a harsh and stressful environment, one which is hypoxic, cold and with little moisture through much of the year. These circumstances should predispose to a variety of pulmonary, cardiovascular and other health problems. Yet he appears surprisingly free of most of these diseases. To what extent is his capacity to survive and thrive contingent upon genetic adaptation, and to what extent upon a sequence of events which are limited to a single lifetime? Answers to these questions could provide important insights into the pathogenesis as well as the natural history of such important disorders as chronic obstructive lung disease and degenerative cardiac disease. This study seeks through the examination of the Aymara, an indigenous people of the Bolivian, Chilean, and Peruvian altiplano, to evaluate the effects of environmental factors, primarily oxygen tension, upon pulmonary function, cardiopulmonary relationships and degenerative heart disease,such as arteriosclerosis, in this unusual population, and to assess the genetic contribution to their anatomical, biochemical and physiological responses to hypoxia.